Bryophytes ruled for <100 million years vascular plants show up ~425mya Plants evolved vascular tissues grow taller than bryophytes connects leaves & roots First vascular plants lacked seeds sperm still need water to swim ferns and lycophytes Fern and lycophyte diversity now diminished
Xylem = water conducting (one way) Phloem = sugar conducting (multi-directional) Conducting cells provide biomechanical support lignin in cell walls does not rot easily does not collapse easily think bundles of rigid straws or pipes Vascular elements move liquid under tension
Vascular tissues belowground extension of ancient stems bryophytes have no ‘true’ roots Absorb water and nutrients active explorers Anchor the plant in place support vertical growth Fossils show roots in lycophytes ~ 400mya convergent evolution in ferns
Photosynthetic organ on plants maximize surface area Microphylls: single unbranched vein unique to lycophytes Megaphylls: leaves with branched veins majority of vascular plants Why does this matter?
Sporophyll: modified leaf with sporangium vastly different looks Trophophyll: vegetative leaf Sporagnium: spore container ferns: clusters of sporagnia called ‘sori’ lycophytes: stobilus holds many sporagnia (like a cone) angiosperms: structures in flowers Spore mother cell: cell inside sporagnium undergoes meiosis to make spores What is the ploidy of each cell type in this picture?
Independent, branched sporophyte Lignified vascular tissue, tracheids & roots tracheid = special xylem cell Leaves are microphylls Some with strobili (evolved multiple times) Some with heterospory (Selaginella/Isoetes) male (micro-) and female (mega-) spores
Whisk Ferns, Equisetum & Ferns mostly homosporous whisk ferns do not have roots Homospory = spores that germinate to produce bisexual (both male and female) gametophytes Leaves are megaphylls whisk ferns lost leaf (enation) Equistem has simplified megaphylls
Whisk Ferns, Equisetum & Ferns mostly homosporous whisk ferns do not have roots Leaves are megaphylls whisk ferns lost leaf (enation) Equistem has simplified megaphylls New Gaga genus with 19 species “We wanted to name this genus for Lady Gaga because of her fervent defense of equality and individual expression” Pryer @ Duke University
One spore → one gametophyte → bisexual gametophyte everything is haploid (1N) Produces both sperm and egg via mitosis A lot of self fertilization What is good/bad about this?
Turn other gametophytes male sperm from everywhere! Archegonia (F) and Antheridia (M) mature at different times
Sporophyte: The fern you see in the woods dominant stage Gametophye: independent haploid generation start out female or bisexual Derived Trait - remember how a moss looks! What does natural selection favor diploid dominant lifecycles?